(Original image from here.)
I was just thinking about how my four main settings offer a different relationship between slavery and Lesbianism:
In "Whips and Stockingtops", Lesbianism is the norm so you get plenty of f/f action, but no transgressive seduction. The good thing is that the slave's presence is taken for granted, so he gets to watch the action.
The world of "The Chastity Belt" is just our world plus a hi-tech CB. Our hero is sort of enslaved, and there are some juicy scenes where vanilla girls get seduced by this, but he's not going to routinely get to watch transgressive Lesbian seductions.
"Chaste Britannia" is my alternate Roman setting. It's quite normal to own a slave, and high-class ladies don't notice them. However, Lesbianism isn't so he does get to watch the seductions.
"Chastity Planet" is a pleasure world. The women who visit the place aren't used to having male slaves, and Lesbianism, when it happens, is transgressive.